Model Output Discussion - 18z 31/10/15 onwards

[knocker]

No sure I totally agree based on model output as it stands for now. Yes, there is a signal from ops and ensembles for a +ve height anomaly to develop  across Labriador/NE Canada and eventually Greenland. But a look at the upper flow charts suggests that the +ve heights will be undercut by a strong jet coming out of N America.

 

You see, there is a split flow regime consistently modelled across N America, which is typical of El Nino conditions, alot of energy going into the STJ which will naturally undercut the ridge over Labrador/greenland area as the jet emerges over the N Atlantic and on towards NW Europe - this keeps troughing/low pressure over mid-Atlantic whilst heights are higher over mainland Europe - not ideal for cold arctic air to spill south across the whole of the UK in any potent way. Though there is, I suppose, a chance of colder air getting in across Scotland at times.

 

 

Yes that was the point I was trying to make in my post #220 along with the EC weeklies.

[IDO]

The JMA update for the last week of November and the first week of December ties in with my thoughts: 

 

No positive height anomalies in our quadrant but a negative height anomaly in the Atlantic, and as the PSEA suggests, a westerly flow, but no turbo charged zonal train IMO. This ties in with the current MJO forecast (appears to be a driver at the moment:

 

  

 

Phase 4 late November before the signal weakens, so a pattern change early December with the El Nino maybe driving the pattern subsequently(?).

 

 

[Nouska]

The JMA update for the last week of November and the first week of December ties in with my thoughts: Y201511.D0412.png

 

No positive height anomalies in our quadrant but a negative height anomaly in the Atlantic, and as the PSEA suggests, a westerly flow, but no turbo charged zonal train IMO. This ties in with the current MJO forecast (appears to be a driver at the moment:

 

realtimemjo.png   NovemberPhase4gt1500mb.gif

 

Phase 4 late November before the signal weakens, so a pattern change early December with the El Nino maybe driving the pattern subsequently(?).

 

Perhaps to the bolded part. Current NWP doesn't progress into phase four at all and the EC32 ends up back in the COD before November end.

 

  

 

Thus slight differences to the composite you linked for >1 Nov - prefer to look at the ENSO positive enhanced composites which are available for winter quarter.

If it does double back to phase two or one, more amplification shown for NE Canada/Greenland sector. Not sure the Euro high, long fetch SWly is a done deal yet.

 

 

[Daniel*]

No sure I totally agree based on model output as it stands for now. Yes, there is a signal from ops and ensembles for a +ve height anomaly to develop  across Labriador/NE Canada and eventually Greenland. But a look at the upper flow charts suggests that the +ve heights will be undercut by a strong jet coming out of N America.

 

You see, there is a split flow regime consistently modelled across N America, which is typical of El Nino conditions, alot of energy going into the STJ which will naturally undercut the ridge over Labrador/greenland area as the jet emerges over the N Atlantic and on towards NW Europe - this keeps troughing/low pressure over mid-Atlantic whilst heights are higher over mainland Europe - not ideal for cold arctic air to spill south across the whole of the UK in any potent way. Though there is, I suppose, a chance of colder air getting in across Scotland at times.

 

NHEM_250_spd_216.gif

 

Unless the jet weakens and buckles upstream to bring a more meridional flow pattern, the Pacific jet is looking rather strong for a while, I find it difficult atm to see potential for much colder weather as we head into 2nd of November for now.

 

But, that's not to say that I it won't happen, just can't see it showing for now from the charts. Trying not to get suckered in by GFS FI teases of +ve height anomalies over Labrador and Greenland or even the GFS AO forecasts dipping neutral, but looking at the wider picture

Cheers...for the assessment Nick, I do not profess to knowing it all rather I'm just a amateur at the bottom end of the spectrum in terms of knowledge, just sharing his thoughts, perhaps it was a dramatised version when the reality is somewhat different. I do not confess to knowing entirely how all these variables interlink and what they mean so take my posts with caution, but I'm trying. I just post what I can interpret it may be quite incorrect although never intentionally however it's a learning process isn't it. I think it can be said some change is afoot and it'll be interesting to see where we end up trickles can lead to rapids further downstream if you see where I'm going...and so that's what is potentially going on I'm not so sure - the environment may not be conducive now and not so distant future but perhaps later it will slot into place, and hey presto we're cooking. On a gut basis I sense something is coming - but that has no place in here. Happy postings.

@fergieweather//@TWOweather to quote UKMO: "Some deterministic output, eg GFS, have a N’ly outbreak for a time, although this is not the preferred solution" 1:15 a.m. - 5 Nov 2015

[seaside 60]

Courtesy MV

 

Week 3 precipitation anomaly map out of the ECMWF Weeklies. Just an El Nino classic. And with the sub-tropical jet roaring out of the southern states next week the Nov. forecast is looking more and more realistic.

However that chart shows only 0 to 20% more than average unless I am reading it wrongly and far less just to the south of us.

So it just shows an average Nov week 3. ??

[Mucka]

Just to say that I wouldn't read too much into today's GFS 12z as it is at odds with its ensembles with the flat jet out of the US

 

 

 

Virtually every ensemble member goes for something more like the control run

 

 

With associated Atlantic ridge which varies in strength from very week to fairly robust.

It could be the associated trough on Eastern flank may be too far West to drag cold air into the UK and only help reinforce heights over Europe which would have the opposite effect of what coldies are looking for and bring in a SW flow for a time.

 

Still a chance of a Northerly outbreak for sure but it doesn't look like the most likely outcome as yet.

[Frosty.]

The Gfs 12z op is a generally very unsettled run with bouts of wet and windy weather for all areas, especially further north and west but the run ends on a high note across southern areas, it's not mild all the time, there are some cooler incursions digging in behind cold fronts and it could occasionally become cold enough next week for showers to turn wintry on higher hills / mountains across scotland and in any quieter interludes between atlantic depressions, there could be slight frosts and fog patches so the main message is it's going to become more seasonal with temperatures closer to where they should be during early to mid november..about time in my opinion!.

Edited November 5, 2015 by Frosty.

[seaside 60]

The Gfs 12z op is a generally very unsettled run with bouts of wet and windy weather for all areas, especially further north and west but the run ends on a high note across southern areas, it's not mild all the time, there are some cooler incursions digging in behind cold fronts and it could occasionally become cold enough next week for showers to turn wintry on higher hills / mountains across scotland and in any quieter interludes between atlantic depressions, there could be slight frosts and fog patches so the main message is it's going to become more seasonal with temperatures closer to where they should be during early to mid november..about time in my opinion!.

If that chart actually happened (ha ha).

The most striking first impression is where is that resident big blue/purple circle to the far left, its sitting due north of the UK.

[nick sussex]

After some convergence this morning the GFS and ECM go their separate ways upstream with wildly different scenarios at T168hrs.

 

Just as the ECM started supporting the GFS the latter has now dropped its original idea, the Canadian high there on the ECM but nowhere to be seen on the GFS at T192hrs.

[Ali1977]

After some convergence this morning the GFS and ECM go their separate ways upstream with wildly different scenarios at T168hrs.

 

Just as the ECM started supporting the GFS the latter has now dropped its original idea, the Canadian high there on the ECM but nowhere to be seen on the GFS at T192hrs.

The Op has dropped it, but there is a lot of support from the GEFS...just a blip from GFS I reckon, I think the next run will have it back.

[Captain Shortwave]

Again the ECM develops the high over NE Canada, but again the result is a sharpening Atlantic trough and the return to more settled but still mild conditions, especially in the south.

 

Still just the occasional GFS operational plus some ensembles going for a northerly, currently no real support from the ECM or GEM. Strangely this could have been the case of the GFS blowing away the high over Canada which just happens to develop a northerly over the UK. So the "eastwards bias" could actually develop the cold solution in this case.

Edited November 5, 2015 by Captain shortwave

[nick sussex]

The Op has dropped it, but there is a lot of support from the GEFS...just a blip from GFS I reckon, I think the next run will have it back.

Even if it does return its still looking a struggle to get the pattern sufficiently se with that Atlantic low looking like causing trouble. At T240hrs on the ECM its like Groundhog Day with the Euro high booking back into the motel ! Any amplification upstream goes all wrong as it just keeps the UK on the eastern side of low pressure. At this point I'd be minded to write off any colder weather for the next 2 weeks. Unless that Atlantic low doesn't phase with low heights near southern Greenland allowing the Canadian high an easier route eastwards then I'm afraid its a no go for any cold.

Edited November 5, 2015 by nick sussex

[joggs]

Still,from a coldie point of view,think about the models showing a tightly wound up vortex the last couple of years at this point. Could be alot worse and also law of averages say we're in for a decent cold spell this winter

[seaside 60]

According the the much maligned CFS that Weather-web use a lot.

From the third week of Nov its Atlantic high and lower heights over Europe, given more of a northerly  and lower than average temps until 2/3rd week in Dec.

Any thoughts...

[phil nw.]

It must be said the next 2 weeks look very Atlantic driven with frequent bands of wind and rain coming through on an active looking jet.

 

One ongoing feature, for southern areas especially, is the remarkable warmth for November expected in the short term,being brought courtesy of the south westerly scourced air(tropical maritme) from the south Atlantic.

 

 

High teens max's are still on the cards over the next few days but of course we pay for it with those rain bands.

 

The ens outputs do hint at some cooling off towards mid-month seen on the Warks. 850hPa graph

and the ens. mean chart at T240hrs.

 

as the mean jet comes a little further south which brings in chances of some colder polar maritme air getting into at least the north.

 

I would say though this would just bring our temperatures closer to normal rather than any suggestion of real cold yet.

We really need to see the jet buckle more upstream to dig some cold air much further south.At the moment things look very mobile and we only see transient ridging being modeled as this comes through between the lows.

Edited November 5, 2015 by phil nw.

[knocker]

The GEFS 6-10 anomaly has weak ridging NE Canada, trough Iceland orientated SW and HP to the SE of the UK. Ergo westerly giving a N/S split weather wise over the UK. The ecm at T240 is not adverse to this scenario with the important exception of ridging over the UK which backs the streamlines and brings the UK much more under the influence of the surface HP.

 

All change with the 11-15 with a ridge over Greenland and the trough north of the UK. This still leaves a westerly airflow but with the jet going on holiday it does increase the options of which one could be some transient northerlies over the UK.

 

It has to be said neither the ecm or NOAA are fully on boards with that interpretation so it's still all systems go for a bumper crop,

http://www.tropicaltidbits.com/

 

 

Edited November 5, 2015 by knocker

[nick sussex]

According the the much maligned CFS that Weather-web use a lot.

From the third week of Nov its Atlantic high and lower heights over Europe, given more of a northerly  and lower than average temps until 2/3rd week in Dec.

Any thoughts...

 Theres just too much error at that range and even if you had the overall NH pattern correct where any block sets up is crucial for the UK, you can have a highly amplified pattern and still be on the wrong side of that amplification. I admits its frustrating as a coldie to watch the Euro high hang on for dear life but its not that unusual and positively we don't see the PV setting up in the " horror" position!

[carinthian]

Good God that latest Exeter charts scares me. I cannot think of a worst chart for cold lovers. Euro high not transient, 564 thickness values embedded in the train of Tm airmass into the Southern UK. Only means one thing for the next 5 days, much the same, 13c day and night, drizzle light rain , gloom and slug pellet conditions for you and cloudless skies for us and snow drought.

 C

[Ali1977]

Good God that latest Exeter charts scares me. I cannot think of a worst chart for cold lovers. Euro high not transient, 564 thickness values embedded in the train of Tm airmass into the Southern UK. Only means one thing for the next 5 days, much the same, 13c day and night, drizzle light rain , gloom and slug pellet conditions for you and cloudless skies for us and snow drought.

 C

brack4.gif

Snow drought at this time of year has probably happened in 99.9 percent of the last 500 years....these charts are fine at this time of year - mid Dec to mid Feb might be slightly more disappointing to cold lovers.

[carinthian]

Snow drought at this time of year has probably happened in 99.9 percent of the last 500 years....these charts are fine at this time of year - mid Dec to mid Feb might be slightly more disappointing to cold lovers.

Yes Ali, its early but many at high altitude have snow cover in November. Presently the Alps are bare above 2500m or more. Of course it could be different by mid- December. This is the driest snow free Autumn many have seen over here, right now. I have lived here for 10 years and never seen the snow level so high.

 C

[Blessed Weather]

Snow drought at this time of year has probably happened in 99.9 percent of the last 500 years....these charts are fine at this time of year - mid Dec to mid Feb might be slightly more disappointing to cold lovers.

 

Hi Ali1977. Carinthian is lucky enough to have a second (possibly his first!) home in the ski resort of Katschberg in Austria. He's over there at the moment so was referring to the lack of snow over there. November is normally the month when the snow arrives in the Alps. But not with that pesky Euro High sticking around!  

 

Edit: Excellent - Carinthian has already replied!

Edited November 5, 2015 by Blessed Weather

[Ali1977]

Hi Ali1977. Carinthian is lucky enough to have a second (possibly his first!) home in the ski resort of Katschberg in Austria. He's over there at the moment so was referring to the lack of snow over there. November is normally the month when the snow arrives in the Alps. But not with that pesky Euro High sticking around!

Edit: Excellent - Carinthian has already replied!

My bad, and as a keen skier I'm watching that area closely...Some Alpine ski seasons are meant to start in late Nov, best a pattern change happen soon if they are to have good skiing available away from Glacial areas. This happened a few years ago when no snow lay below 2000m, then many resorts had such big dumps late Nov they had to call a curfew on people being outside!! Fingers crossed. Edited November 5, 2015 by Ali1977

[london and south east kent]

Just seen bbc 10 day look ahead there saying it may get colder with frost mid November onwards with a northerly ..maybe.😊

Edited November 5, 2015 by abbie123456

[johnholmes]

not really what he said, 'less mild, drier, was what I heard, no mention of a northerly unless I missed that?

 

the link see what you believe John Hammond said

http://www.bbc.co.uk/weather/features/34741548

Edited November 5, 2015 by johnholmes

[london and south east kent]

Hi yes I was mistakin winds from north and west dryer too with frost thanks John 😊

Edited November 5, 2015 by abbie123456